Abstract: An electrohydraulic system for bending tube stock includes a bend head having a mandrel and an actuator coupled to a bending die for engaging the tube stock and bending the stock around the mandrel. A clamp is coupled to a second actuator for gripping the tube stock, and a third actuator mechanism in the form of a boost cylinder is coupled to the clamp for urging the tube stock lengthwise into the bend head. An electrohydraulic valve is responsive to an electronic valve control signal for variably feeding hydraulic fluid to the boost cylinder, and velocity of slip at the clamp is determined. An input pressure command signal is compared with pressure at the boost cylinder to develop a pressure error signal. Slip velocity is compared with a velocity limit command to develop a velocity difference when slip velocity exceeds the velocity limit, and the pressure error signal is modulated and employed as the valve command signal to maintain slip velocity at or below the level of the velocity limit command.

Abstract: An electrohydraulic system for bending tube stock includes a bend head having a mandrel and an actuator coupled to a bending die for engaging the tube stock and bending the stock around the mandrel. A clamp is coupled to a second actuator for gripping the tube stock, and a third actuator mechanism in the form of a boost cylinder is coupled to the clamp for urging the tube stock lengthwise into the bend head. An electrohydraulic valve is responsive to an electronic valve control signal for variably feeding hydraulic fluid to the boost cylinder, and velocity of slip at the clamp is determined. An input pressure command signal is compared with pressure at the boost cylinder to develop a pressure error signal. Slip velocity is compared with a velocity limit command to develop a velocity difference when slip velocity exceeds the velocity limit, and the pressure error signal is modulated and employed as the valve command signal to maintain slip velocity at or below the level of the velocity limit command.

Abstract: An electrohydraulic system includes a plurality of electrohydraulic devices individually controlled by on-board microprocessor-based control electronics. Each individual device controller is connected to and addressable by a master controller for coordinating operation of the various devices. An electrohydraulic servo valve assembly includes a hydraulic manifold having a valve spool variably positionable therein under control of a torque motor. A microprocessor-based controller is connected to the torque motor and is mounted on the manifold by a cover which encloses and protects both the controller and the torque motor. A watchdog timer in the microprocessor-based controller monitors pulsewidth modulated signals to the torque motor for terminating operation in the event of signal loss. In a preferred embodiment of the invention, the servo valve assembly is coupled to a linear actuator which has its position monitored by an electroacoustic transducer.